add links to testing examples

Author: yyx990803

src/guide/application.md

@@ -175,6 +175,8 @@ describe('my-component', function () {
 })
 ```
 
+There are example Karma configurations for both [Webpack](https://github.com/vuejs/vue-loader-example/blob/master/build/karma.conf.js) and [Browserify](https://github.com/vuejs/vueify-example/blob/master/karma.conf.js).
+
 <p class="tip">Since Vue.js directives perform updates asynchronously, when you are asserting DOM state after changing the data, you will have to do so in a `Vue.nextTick` callback.</p>
 
 ## Deploying for Production